Video: See our full interview with Apollo 7 astronaut Walt Cunningham

Around NASA and its contractors, the phrase "Return to Flight" carries special meaning. It's used very seriously in very specific circumstances: a "Return to Flight" mission is a resumption of normal scheduled missions after an anomaly or accident. Most recently, the phrase was used to refer to the 2005 STS-114 and STS-121 shuttle flights, which were the first missions to take flight from the Kennedy Space Center following the destruction of Columbia in early 2003. Prior to that, STS-26 was the "Return to Flight" mission in the aftermath of the Challenger disaster in 1986.

But the big granddaddy of Returns to Flight was Apollo 7 in October 1968. Mindful of Kennedy's end-of-decade deadline for a lunar landing, NASA's engineers and astronauts had to fight through a complex admixture of both cautiousness and eagerness—they needed to get back into space as soon as possible, but they also needed to make sure they weren't going to kill anyone else. The job of commanding Apollo 7 landed on Mercury veteran Walter "Wally" Schirra and his rookie crew—Donn Eisele and Ronnie Walter Cunningham.